Transmission And Radiation Characteristics Of Surface Plasmonic Devices In Microwave Frequencies

Surface Plasmon Polaritons(SPP)are special electromagnetic waves formed by the resonant coupling of light waves and surface electrons on metal surface,which can be bound to the interface between metal and dielectric for transmission.The SPP can be applied to the microwave or THz band by constructing periodic holes on the metal surface.This electromagnetic mode is called Spoof Surface Plasmon Polaritons(SSPP).SSPP has similar characteristics to SPP in the optical band.Adjusting the parameters of the periodic structure can affect the dispersion characteristics of SSPP,which provides a new idea for the design of future intelligent and controllable circuits.Three different unit structures are designed in this paper.Based on them,corresponding waveguides,filters,and antennas are constructed and their performances are discussed in detail.The main contents are as follows.Firstly,an asymmetrical serrated unit structure was proposed and SSPP microwave waveguide was designed based on it.The influence of transverse branch length e of the periodic unit on the dispersion characteristics is simulated.At the same time,SSPP waveguides with different e values are designed.The simulated and measured results are also compared,which well reflects the controllability of SSPP.By observing the current distribution on the waveguide surface,we analyze the principle that the transverse branch length affects the bandwidth.Then,a SSPP microwave waveguide based on T-shaped branch units is designed.We analyze the differences of field confinement and loss at different frequencies.Based on the waveguide,we load the split ring resonator around the T-shaped branch to acquire the stop-band and analyze the effect of the end branch length Re on its stopband frequency.We realize wideband of the stop-band by increasing the number of split ring resonators with gradually changing geometric parameters.The experimental results show that the filters have good filtering functions in the corresponding stopband range.Finally,the periodic unit loaded with rectangular ring cavities is proposed and a SSPP microwave waveguide is designed based on it.We make truncation gaps on the surface of the waveguide to design two types of SSPP leaky wave antennas.They achieve the transition from SSPP mode to radiation mode through the gradual change of the gap width or the period height.In order to reduce the size of the antenna,the antenna is also halved to form a single-port antenna structure.The simulated results under the situations of dual-port and single-port show that the designed antennas have a wide bandwidth,high efficiency and good directivity.Not only that,they also have a beam frequency sweep function.